The invention relates to an on-line wash system for a compressor in a gas turbine or other turbomachine.
Spraying water into the inlet of a compressor of a gas turbine is a commonly used technique to wash the compressor and remove dirt and other material from the surfaces of the compressor, and particularly from the surfaces of the blades of the compressor. The wash systems are on-line in the sense that they inject water into the compressor while the gas turbine is operating.
Conventional on-line wash systems inject water into the air flow passing through a bell mouth casing mounted to the inlet of a compressor. The bell mouth inlet casing has interior and exterior walls that define an air passage (also referred to as an air plenum) leading to the inlet of the compressor.
Nozzles are typically mounted on the walls of the bell mouth casing. The nozzles spray water into the air flowing through the bell mouth casing. The spray forms water droplets that enter the compressor. Droplets migrate towards streams of relatively low velocity of the air such as streams moving along the walls of the bell mouth casing. Accordingly, the density of water droplets increases in streams of low velocity air.
The droplets have mass and impact forcibly against the rotating blades of the compressor, especially the first stage blades that are nearest the inlet. The impacts of the droplets can pit and erode the blades. The pitting and erosion may be greatest at the roots of the blades which are exposed to the high density of droplets in the slower streams moving along the walls of the bell mouth casing. The droplets impacting the rotor blades may over time cause in pitting and erosion of the blades, particularly at the roots of the blades.